The monarch began her conversation with Commander Lucy D'Orsi by quipping "oh, bad luck" when a palace official described how the officer had been assigned as Gold Commander for the state visit of Chinese premier Xi Jinping in October.

During the discussion recorded by a BBC cameraman, the official was heard telling the Queen the police had been "seriously undermined by the Chinese" in their handling of the visit, but the officer had managed to "hold her own".

WPA Pool via Getty Images

The Queen talking to David Cameron earlier in the day

As Ms D'Orsi asked if she knew it had been a "testing time", the Queen interjected: "I did."

The officer described how Chinese officials walked out of a meeting with Barbara Woodward, British ambassador to China, at Lancaster House, telling them the trip was off.

The Queen said: "They were very rude to the ambassador."

The remarks were recorded as the Queen greeted guests in the gardens of Buckingham Palace for an event marking her 90th birthday, reports the Press Association.

In China, BBC World coverage of the remarks was censored.

Chinese censors are blocking @BBCWorld reports about HMTQ comments that #xijinping officials were 'very rude' during last year state visit

The Metropolitan Police said it would not comment on the private conversation.

Speaking on BBC Radio 4's Today Programme, Kerry Brown, a former First Secretary at the British Embassy in Beijing, said that the comments showed the "tension and effort" which lay beneath the surface of the event.

He said: "It shows that these meetings when they look so good there is underneath obviously a huge amount of tension and effort."

However, Brown did not believe that the incident was a major issue and said: "This is nothing more than a bit of entertaining sideshow."

Former Liberal Democrat leader Menzies Campbell echoed his views.

He said that there would be "irritation" both at the Palace and in government.

He added: "I don’t think there will be any lasting damage but it’s an irritation and it’s an irritation people could do without."